A optical system of a head mounted display (HMD) system that includes a lens assembly comprising a first lens element and a second lens element that are directly or indirectly coupled together, for example, via a suitable optically clear adhesive. The lens assembly may include a quarter-wave plate disposed between the first and second lens elements. The first lens element may include a surface with an anti-reflective coating thereon, and the second lens element may include a surface with a partially reflective coating thereon. The optical system may include a reflective polarizer that, together with the lens assembly, focuses light from a display system to an eye of a user of the head mounted display system.